In line with EC regulation No 3821/85, in future the tachographs used in commercial vehicles to record operating data will no longer, as conventionally, use analogue means to write on a paper tachograph disk but rather will store the speed over time digitally in a data store, namely a data store on a data card. The EC regulation contains extensive details as to how the data to be recorded, which need to meet the requirements for legal evidence, inter alia, are to be stored and to be protected against manipulation. To meet the stringent requirements of the regulation, very complex cryptological protection mechanisms and authentication processes need to be implemented. Particular focus in this context is on allowing the transmission of data between the data store on the data card and the tachograph. A data card holding apparatus is already the subject matter of German laid-open specification DE 103 21 252 A1, which describes an antimanipulation holder for a card in a tachograph as described above. Particularly the transmission of data between the data store on the data card and a memory in the tachograph needs to be protected against manipulation, since experience shows that such attacks are to be feared in this area. For this reason, pertinent tachographs and data cards respectively provide an encryption unit as an integral component which is used to transmit data in cryptologically protected form exclusively using a session key. This protection is extremely complex, however, and requires a lot of patience from the user, since access times are extended almost intolerably on account of the protection of the data transmission between the tachograph and the data card. In line with ISO 7816, the read/write access to the data store on the data card is furthermore limited to a length of 256 bytes, which means that the communication via the serial connection used at this location takes place very slowly on the basis of the EC regulation.